This invention relates to power converters, and more particularly to isolated dc to dc power converters, though an alternative embodiment of the invention is adapted for isolated ac to ac power conversion.
A generic block diagram of a representative isolated de to de power converter 181 is shown in FIG. 18. In the center is a high frequency transformer 182. As is the nature of most transformers, the excitation is ac, and that is provided by a switching network 183. The output of the transformer also is ac, requiring rectification to provide a dc output. The rectifier may be a synchronous rectifier 184. Both the input switching network 183 and the rectifier 184 tend to generate significant electrical noise, so input and output inductors 185 and 186 usually are needed. Very likely, there will be an input filter capacitor 187 and an output filter capacitor 188.
The symmetrical power converter builds on the teachings of the symmetrical push-pull transformer from 1990, best explained by reference to “Design and Application of Matrix Transformers and Symmetrical Converters,” a tutorial for a seminar presented at the Fifth International High Frequency Power Conversion Conference '90 in Santa Clara, Calif., on May 11, 1990. The symmetrical push-pull had limited commercial success, but it is quite difficult to provide suitable drive for its semiconductor switches.